Memory device and method for fabricating the same

Abstract

An integrated circuit device includes a ferroelectric layer that is formed with chlorine-free precursors. This ferroelectric material may be of the composition HFxZr1-xO2. The ferroelectric layer may be used in a memory device such as a ferroelectric field effect transistor (FeFET). A ferroelectric layer formed with chlorine-free precursors has no chlorine residue. The absence of chlorine ameliorates time-dependent dielectric breakdown (TDDB) and Bias Temperature Instability (BTI).

What is claimed is: 
     
       1. A method of forming an integrated circuit device, the method comprising:
 forming a ferroelectric layer by an atomic layer deposition (ALD process) using chlorine-free precursors, wherein the ferroelectric layer has a top surface that results from the ALD process and the chlorine-free precursors comprise a hafnium (Hf) compound and a zirconium (Zr) compound; 
 prior to any further processing of the ferroelectric layer subsequent to the ALD process, depositing either a dielectric layer-metal oxide semiconductor layer stack, a metal oxide semiconductor layer, or a top electrode layer directly over and in contact with the top surface. 
 
     
     
       2. The method of  claim 1 , wherein the chlorine-free precursors further comprise a compound of aluminum (Al), silicon (Si), lanthanum (La), scandium (Sc), calcium (Ca), barium (Ba), gadolinium (Gd), or yttrium (Y). 
     
     
       3. The method of  claim 1 , wherein the chlorine-free precursors are compounds in which nitrogen is bonded to a metal. 
     
     
       4. The method of  claim 1 , wherein the chlorine-free precursors are compounds in which carbon is bonded to a metal. 
     
     
       5. The method of  claim 1 , wherein the chlorine-free precursors are compounds of a form M-(N—R) n , wherein M is a metal, R is one or more organic functional groups, and n is an integer. 
     
     
       6. A method of forming an integrated circuit device, the method comprising:
 forming a bottom electrode layer in or on a substrate; 
 forming a ferroelectric layer having a top surface directly over the bottom electrode layer by an atomic layer deposition process that includes repeating steps comprising:
 exposing the substrate to an evaporated zirconium (Zr) compound that is chlorine-free and forms a first surface layer; 
 exposing the substrate to a first gas so that the first gas reacts with the first surface layer to form a zirconium-containing layer; 
 exposing the substrate to an evaporated hafnium (Hf) compound that is chlorine-free and forms a second surface layer; 
 exposing the substrate to the first gas so that the first gas reacts with the second surface layer to form a hafnium-containing layer; 
 
 forming either a dielectric layer-metal oxide semiconductor layer stack, a metal oxide semiconductor layer, or a top electrode layer directly over and in contact with the top surface that is uppermost in the ferroelectric layer at the conclusion of the atomic layer deposition process. 
 
     
     
       7. The method of  claim 6 , wherein the ferroelectric layer has less than 1 PPM chlorine. 
     
     
       8. The method of  claim 6 , wherein:
 a structure comprising the bottom electrode layer, the ferroelectric layer, and the top electrode layer has a leakage current and a time-dependent dielectric breakdown (TDDB) rate; 
 the TDDB rate is less than an amount by which the TDDB rate would increase if 1 PPM of chlorine were added to the ferroelectric layer; and 
 the TDDB rate is defined as an initial value of the leakage current divided by a time of operation over which the leakage current doubles from the initial value. 
 
     
     
       9. The method of  claim 6 , wherein the evaporated zirconium compound (Zr) and the evaporated hafnium compound (Hf) are of a form M-(N—R 1 R 2 ) n , wherein M is a metal, R 1  and R 2  are organic functional groups, and n is an integer. 
     
     
       10. The method of  claim 6 , wherein the evaporated zirconium compound (Zr) and the evaporated hafnium compound (Hf) are metals bonded to functional groups through oxygen, carbon, or oxygen and carbon. 
     
     
       11. A method of forming an integrated circuit device, the method comprising:
 forming a bottom electrode layer; 
 forming by atomic layer deposition from chlorine-free gaseous metal precursors comprising a zirconium (Zr) precursor and a hafnium (Hf) precursor a ferroelectric layer with an upper surface directly over the bottom electrode layer; and 
 immediately after the atomic layer deposition process, forming either a dielectric layer-metal oxide semiconductor layer stack, a metal oxide semiconductor layer, or a top electrode layer over and in direct contact with the upper surface, wherein the chlorine-free gaseous metal precursors are metals bonded with organic functional groups via oxygen, carbon, or nitrogen. 
 
     
     
       12. The method of  claim 11 , wherein the ferroelectric layer has less than 1 PPM chlorine. 
     
     
       13. The method of  claim 1 , wherein the method comprises depositing the dielectric layer-metal oxide semiconductor layer stack directly over and in contact with the top surface. 
     
     
       14. The method of  claim 1 , wherein the method comprises depositing the top electrode layer over and in direct contact with the top surface. 
     
     
       15. The method of  claim 6 , wherein forming the ferroelectric layer further comprises exposing the substrate to a chlorine-free precursors of aluminum (Al), silicon (Si), lanthanum (La), scandium (Sc), calcium (Ca), barium (Ba), gadolinium (Gd), or yttrium (Y). 
     
     
       16. The method of  claim 6 , wherein the method comprises forming the dielectric layer-metal oxide semiconductor layer stack directly over and in contact with the top surface. 
     
     
       17. The method of  claim 6 , wherein the method comprises forming the top electrode layer directly over and in contact with the top surface. 
     
     
       18. The method of  claim 11 , wherein the chlorine-free gaseous metal precursors further comprise a compound of aluminum (Al), silicon (Si), lanthanum (La), scandium (Sc), calcium (Ca), barium (Ba), gadolinium (Gd), or yttrium (Y). 
     
     
       19. The method of  claim 11 , wherein the method comprises forming the dielectric layer-metal oxide semiconductor layer stack over and in direct contact with the upper surface. 
     
     
       20. The method of  claim 11 , wherein the method comprises forming the top electrode layer over and in direct contact with the upper surface.